WIRELESS ENERGY TRANSFER

• US 20080278264A1
• Filed: 03/26/2008
• Published: 11/13/2008
• Est. Priority Date: 07/12/2005
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Karalis, Aristeidis, Soljacic, Marin, Moffatt, Robert, Kurs, Andre B., Joannopoulos, John D., Fisher, Peter H.
• Granted Patent: US 7,825,543 B2
• Time in Patent Office: Days
• US Class Current: 333/219
• CPC Class Codes: B60L 2210/20 AC to AC converters
• CPC Class Codes: B60L 53/126 Methods for pairing a vehicle and a charging station, e.g. establishing a one-to-one relation between a wireless power transmitter and a wireless power receiver
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 9/04 Resonant antennas
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor

Abstract

Disclosed is an apparatus for use in wireless energy transfer, which includes a first resonator structure configured to transfer energy non-radiatively with a second resonator structure over a distance greater than a characteristic size of the second resonator structure. The non-radiative energy transfer is mediated by a coupling of a resonant field evanescent tail of the first resonator structure and a resonant field evanescent tail of the second resonator structure.

Claims

1. An apparatus for use in wireless energy transfer, the apparatus comprising:

a first resonator structure configured for energy transfer with a second resonator structure, over a distance D larger than a characteristic size L₁ of said first resonator structure and larger than a characteristic size L₂ of said second resonator structure,

wherein the energy transfer has a rate K and is mediated by evanescent-tail coupling of a resonant field of the first resonator structure and a resonant field of the second resonator structure, wherein

said resonant field of the first resonator structure has a resonance angular frequency ω

₁, a resonance frequency-width Γ

₁, and a resonance quality factor Q₁=ω

₁/2Γ

₁ at least larger than 300, and

said resonant field of the second resonator structure has a resonance angular frequency ω

₂, a resonance frequency-width Γ

₂, and a resonance quality factor Q₂=ω

₂/2Γ

₂ at least larger than 300,

wherein the absolute value of the difference of said angular frequencies ω

₁ and ω

₂ is smaller than the broader of said resonant widths Γ

₁ and Γ

₂, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 20.

2. The apparatus of claim 1, wherein Q, is at least larger than 1000, Q₂ is at least larger than 1000, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 50.

3. The apparatus of claim 1, wherein D/L₂ is at least larger than 5, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 2.

4. The apparatus of claim 1, wherein D/L₂ is at least larger than 5, Q, is at least larger than 1000, Q₂ is at least larger than 1000, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 5.

5. The apparatus of claim 1, wherein D/L₂ is at least larger than 10, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 0.4.

6. The apparatus of claim 1, wherein D/L₂ is at least larger than 10, Q, is at least larger than 1000, Q₂ is at least larger than 1000, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 1.

7. The apparatus of claim 1, wherein the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is maximized at an angular frequency {tilde over (ω

)} with a frequency width {tilde over (Γ

)}, and

the absolute value of the difference of the angular frequencies ω

₁ and {tilde over (ω

)} is smaller than the width {tilde over (Γ

)}, and

the absolute value of the difference of the angular frequencies ω

₂ and {tilde over (ω

)} is smaller than the width {tilde over (Γ

)}.

8. The apparatus of claim 1, further comprising the second resonator structure.

9. The apparatus of claim 1, wherein a device coupled to the first or second resonator structure with a coupling rate Γ

_work receives from the resonator structure, to which it is coupled, a usable power P_work at least larger than 0.03 Watt.

10. The apparatus of claim 9, wherein P_work is at least larger than 1 Watt.

11. The apparatus of claim 9, wherein P_work is at least larger than 30 Watt.

12. The apparatus of claim 9, wherein, if the device is coupled to the first resonator, the quantity [(Γ

_work/Γ

₁)²−

1]/(κ

/√

{square root over (Γ

₁Γ

₂)})² is at least larger than 0.5 and smaller than 2, and if the device is coupled to the second resonator, the quantity [(Γ

_work/Γ

₂)²−

1]/(κ

/√

{square root over (Γ

₁Γ

₂)})² is at least larger than 0.5 and smaller than 2.

13. The apparatus of claim 9, wherein the device comprises at least one of a robot, a mobile electronic device, a computer, a sensor, a vehicle, a medical device configured to be implanted in a patient, a television screen, a wireless keyboard, and a wireless mouse.

14. The apparatus of claim 9, further comprising the device.

15. The apparatus of claim 9, wherein, during operation, a power supply coupled to the first or second resonator structure with a coupling rate Γ

_supply drives the resonator structure, to which it is coupled, at a frequency f and supplies power P_total, wherein

the absolute value of the difference of the angular frequencies ω

=2π

f and ω

₁ is smaller than the resonant width Γ

₁, and

the absolute value of the difference of the angular frequencies ω

=2π

f and ω

₂ is smaller than the resonant width Γ

₂.

16. The apparatus of claim 15, wherein, if the power supply is coupled to the first resonator, the quantity [(Γ

_supply/Γ

₁)²−

1]/(κ

/√

{square root over (Γ

₁Γ

₂)})² is at least larger than 0.5 and smaller than 2, and if the power supply is coupled to the second resonator, the quantity [(Γ

_supply/Γ

₂)²−

1]/(κ

/√

{square root over (Γ

₁Γ

₂)})² is at least larger than 0.5 and smaller than 2.

17. The apparatus of claim 15, further comprising the power supply.

18. The apparatus of claim 15, wherein, during the energy exchange, power P_rad is radiated and the radiation loss η

_rad=P_rad/P_total is less that 10%.

19. The apparatus of claim 15, wherein, during the energy exchange, power P_rad is radiated and the radiation loss η

_rad=P_rad/P_total, is less that 1%.

20. The apparatus of claim 1, wherein the resonant fields are electromagnetic.

21. The apparatus of claim 20, wherein f is at least larger than 100 kHz and smaller than 500 MHz.

22. The apparatus of claim 20, wherein f is at least larger than 1 MHz and smaller than 50 MHz.

23. The apparatus of claim 20, wherein f is within one of the frequency bands specially assigned for industrial, scientific, and medical (ISM) equipment.

24. The apparatus of claim 20, wherein the resonant fields are primarily magnetic at a distance D_p from the center of the closest resonant object, whose characteristic size is L_R, and the ratio of the average electric field energy density to the average magnetic field energy density is smaller than 0.1 for D_p/L_R less than 3.

25. The apparatus of claim 20, wherein the resonant fields are primarily magnetic at a distance D_p from the center of the closest resonant object, whose characteristic size is L_R, and the ratio of the average electric field energy density to the average magnetic field energy density is smaller than 0.01 for D_p/L_R less than 3.

26. The apparatus of claim 20, wherein at least one of the first and second resonator structures comprises a self resonant coil of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon.

27. The apparatus of claim 26, wherein the resonator structure receiving energy from the other resonator structure comprises a self resonant coil of conducting wire,

wherein said coil is helical, the radius of said coil is about 10 cm, the height of said coil is about 3 cm, the number of turns of said coil is about 6, and the radius of said conducting wire is about 2 mm.

28. The apparatus of claim 26, wherein the resonator structure receiving energy from the other resonator structure comprises a self resonant coil of conducting wire,

wherein said coil is helical, the radius of said coil is about 30 cm, the height of said coil is about 20 cm, the number of turns of said coil is about 5.25, and the radius of said conducting wire is about 3 mm.

29. The apparatus of claim 20, wherein at least one of the first and second resonator structures comprises a capacitively loaded loop or coil of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon.

30. The apparatus of claim 29, wherein the resonator structure receiving energy from the other resonator structure comprises a capacitively loaded loop of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon,

wherein the characteristic size of said loop is less than 10 cm and the width of said conducting wire or Litz wire or ribbon is less than 1 cm.

31. The apparatus of claim 29, wherein the resonator structure receiving energy from the other resonator structure comprises a capacitively loaded loop of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon,

wherein the characteristic size of said loop is less than 30 cm and the width of said conducting wire or Litz wire or ribbon is less than 5 cm.

32. The apparatus of claim 20, wherein at least one of the first and second resonator structures comprises an inductively loaded rod of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon.

33. The apparatus of claim 32, wherein the resonator structure receiving energy from the other resonator structure comprises an inductively loaded rod of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon,

wherein the characteristic size of said rod is less than 10 cm and the width of said conducting wire or Litz wire or ribbon is less than 1 cm.

34. The apparatus of claim 32, wherein the resonator structure receiving energy from the other resonator structure comprises an inductively loaded rod of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon,

wherein the characteristic size of said rod is less than 30 cm and the width of said conducting wire or Litz wire or ribbon is less than 5 cm.

35. The apparatus of claim 1, further comprising a feedback mechanism for maintaining the resonant frequency of one or more of the resonant objects.

36. The apparatus of claim 35, wherein the feedback mechanism comprises an oscillator with a fixed frequency and is configured to adjust the resonant frequency of the one or more resonant objects to be about equal to the fixed frequency.

37. The apparatus of claim 35, where the feedback mechanism is configured to monitor an efficiency of the energy transfer, and adjust the resonant frequency of the one or more resonant objects to maximize the efficiency.

38. An apparatus for use in wireless energy transfer, the apparatus comprising:

a first resonator structure configured for energy transfer with a second resonator structure, over a distance D larger than a characteristic thickness T₁ of said first resonator structure and larger than a characteristic size L₂ of said second resonator structure,

wherein the energy transfer has a rate K and is mediated by evanescent-tail coupling of a resonant field of the first resonator structure and a resonant field of the second resonator structure, wherein

said resonant field of the first resonator structure has a resonance angular frequency ω

₁, a resonance frequency-width Γ

₁, and a resonance quality factor Q₁=ω

₁/2Γ

₁ at least larger than 300, and

said resonant field of the second resonator structure has a resonance angular frequency ω

₂, a resonance frequency-width Γ

₂, and a resonance quality factor Q₂=ω

₂/2Γ

₂ at least larger than 300,

wherein the absolute value of the difference of said angular frequencies ω

₁ and ω

₂ is smaller than the broader of said resonant widths Γ

₁ and Γ

₂, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 20.

39. The apparatus of claim 38, wherein Q₁ is at least larger than 1000, Q₂ is at least larger than 1000, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 50.

40. The apparatus of claim 38, wherein D/L₂ is at least larger than 5, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 2.

41. The apparatus of claim 38, wherein D/L₂ is at least larger than 5, Q₁ is at least larger than 1000, Q₂ is at least larger than 1000, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 5.

42. The apparatus of claim 38, wherein D/L₂ is at least larger than 10, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 0.4.

43. The apparatus of claim 38, wherein D/L₂ is at least larger than 10, Q₁ is at least larger than 1000, Q₂ is at least larger than 1000, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 1.

44. The apparatus of claim 38, wherein the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is maximized at an angular frequency {tilde over (ω

)} with a frequency width {tilde over (Γ

)}, and

the absolute value of the difference of the angular frequencies ω

₁ and {tilde over (ω

)} is smaller than the width F, and

the absolute value of the difference of the angular frequencies ω

₂ and {tilde over (ω

)} is smaller than the width {tilde over (Γ

)}.

45. The apparatus of claim 38, further comprising the second resonator structure.

46. The apparatus of claim 38, wherein a device coupled to the first or second resonator structure with a coupling rate Γ

_work receives from the resonator structure, to which it is coupled, a usable power P_work at least larger than 0.03 Watt.

47. The apparatus of claim 46, wherein P_work is at least larger than 1 Watt.

48. The apparatus of claim 46, wherein P_work is at least larger than 30 Watt.

49. The apparatus of claim 46, wherein, if the device is coupled to the first resonator, the quantity [(Γ

_work/Γ

₁)²−

1]/(κ

/√

{square root over (Γ

₁Γ

₂)})² is at least larger than 0.5 and smaller than about 2, and if the device is coupled to the second resonator, the quantity [(F_work/Γ

₂)²−

1]/(κ

/√

{square root over (Γ

₁Γ

₂)})² is at least larger than 0.5 and smaller than about 2.

50. The apparatus of claim 46, wherein the device comprises at least one of a robot, a mobile electronic device, a computer, a sensor, a vehicle, a medical device configured to be implanted in a patient, a television screen, a wireless keyboard, and a wireless mouse.

51. The apparatus of claim 46, further comprising the device.

52. The apparatus of claim 46, wherein, during operation, a power supply coupled to the first or second resonator structure with a coupling rate Γ

_supply drives the resonator structure, to which it is coupled, at a frequency f and supplies power P_total, wherein

the absolute value of the difference of the angular frequencies ω

=2π

f and ω

₁ is smaller than the resonant width Γ

₁, and

the absolute value of the difference of the angular frequencies ω

=2π

f and ω

₂ is smaller than the resonant width Γ

₂.

53. The apparatus of claim 52, wherein, if the power supply is coupled to the first resonator, the quantity [(Γ

_supply/Γ

₁)²−

1]/(κ

K/√

{square root over (Γ

₁Γ

₂)})² is at least larger than 0.5 and smaller than about 2, and if the power supply is coupled to the second resonator, the quantity [(Γ

_supply/Γ

₂)²−

1]/(κ

/√

{square root over (Γ

₁Γ

²)})² is at least larger than 0.5 and smaller than about 2.

54. The apparatus of claim 52, further comprising the power supply.

55. The apparatus of claim 52, wherein, during the energy exchange, power P_rad is radiated and the radiation loss η

_rad=P_rad/P_total is less that 10%.

56. The apparatus of claim 52, wherein, during the energy exchange, power P_rad is radiated and the radiation loss η

_rad=P_rad/P_total, is less that 1%.

57. The apparatus of claim 38, wherein the resonant fields are electromagnetic.

58. The apparatus of claim 57, wherein f is at least larger than 100 kHz and smaller than 500 MHz.

59. The apparatus of claim 57, wherein f is at least larger than 1 MHz and smaller than 50 MHz.

60. The apparatus of claim 57, wherein f is within one of the frequency bands specially assigned for industrial, scientific and, medical (ISM) equipment.

61. The apparatus of claim 57, wherein the resonant fields are primarily magnetic at a distance D_p from the center of the closest resonant object, whose characteristic size is L_R, and the ratio of the average electric field energy density to the average magnetic field energy density is smaller than about 0.1 for D_p/L_R less than 3.

62. The apparatus of claim 57, wherein the resonant fields are primarily magnetic at a distance D_p from the center of the closest resonant object, whose characteristic size is L_R, and the ratio of the average electric field energy density to the average magnetic field energy density is smaller than about 0.01 for D_p/L_R less than 3.

63. The apparatus of claim 57, wherein at least one of the first and second resonator structures comprises a capacitively loaded loop or coil of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon.

64. The apparatus of claim 63, wherein the resonator structure receiving energy from the other resonator structure comprises a capacitively loaded loop of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon,

wherein the characteristic size of said loop is less than 10 cm and the width of said conducting wire or Litz wire or ribbon is less than 1 cm.

65. The apparatus of claim 63, wherein the resonator structure receiving energy from the other resonator structure comprises a capacitively loaded loop of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon,

wherein the characteristic size of said loop is less than 30 cm and the width of said conducting wire or Litz wire or ribbon is less than 5 cm.

66. The apparatus of claim 57, wherein at least one of the first and second resonator structures comprises an inductively loaded rod of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon.

67. The apparatus of claim 66, wherein the resonator structure receiving energy from the other resonator structure comprises an inductively loaded rod of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon,

wherein the characteristic size of said rod is less than 10 cm and the width of said conducting wire or Litz wire or ribbon is less than 1 cm.

68. The apparatus of claim 66, wherein the resonator structure receiving energy from the other resonator structure comprises an inductively loaded rod of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon,

wherein the characteristic size of said rod is less than 30 cm and the width of said conducting wire or Litz wire or ribbon is less than 5 cm.

69. The apparatus of claim 38, further comprising a feedback mechanism for maintaining the resonant frequency of one or more of the resonant objects.

70. The apparatus of claim 69, wherein the feedback mechanism comprises an oscillator with a fixed frequency and is configured to adjust the resonant frequency of the one or more resonant objects to be about equal to the fixed frequency.

71. The apparatus of claim 69, where the feedback mechanism is configured to monitor an efficiency of the energy transfer, and adjust the resonant frequency of the one or more resonant objects to maximize the efficiency.

72. A method for wireless energy transfer, the method comprising:

providing a first resonator structure and transferring energy with a second resonator structure, over a distance D larger than a characteristic size L₁ of said first resonator structure and larger than a characteristic size L₂ of said second resonator structure,

wherein the energy transfer has a rate κ and

is mediated by evanescent-tail coupling of a resonant field of the first resonator structure and a resonant field of the second resonator structure, wherein

said resonant field of the first resonator structure has a resonance angular frequency ω

₁, a resonance frequency-width Γ

₁, and a resonance quality factor Q₁=ω

₁/2Γ

₁ at least larger than 300, and

said resonant field of the second resonator structure has a resonance angular frequency ω

₂, a resonance frequency-width Γ

₂, and a resonance quality factor Q₂=ω

₂2/2Γ

₂ at least larger than 300,

wherein the absolute value of the difference of said angular frequencies ω

₁ and ω

₂ is smaller than the broader of said resonant widths Γ

₁ and Γ

₂, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 20.

73. A method for wireless energy transfer, the method comprising:

providing a first resonator structure and transferring energy with a second resonator structure, over a distance D larger than a characteristic thickness T₁ of said first resonator structure and larger than a characteristic size L₂ of said second resonator structure,

wherein the energy transfer has a rate κ and

is mediated by evanescent-tail coupling of a resonant field of the first resonator structure and a resonant field of the second resonator structure, wherein

said resonant field of the first resonator structure has a resonance angular frequency ω

₁, a resonance frequency-width Γ

₁, and a resonance quality factor Q₁=ω

₁/2Γ

₁ at least larger than 300, and

said resonant field of the second resonator structure has a resonance angular frequency ω

₂, a resonance frequency-width Γ

₂, and a resonance quality factor Q₂=ω

₂/2Γ

₂ at least larger than 300,

wherein the absolute value of the difference of said angular frequencies ω

₁ and ω

₂ is smaller than the broader of said resonant widths Γ

₁ and Γ

₂, and the quantity κ

/√

{square root over (Γ

₁Γ

₂)} is at least larger than 20.